In the oil production industry, an oil well is typically drilled hundreds or thousands of feet within various geological strata to reach a permeable formation containing an oil reservoir. Such permeable formations include any subsurface or subterranean media through which a fluid (e.g. oil or water) may flow, including but not limited to soils, sands, shales, porous rocks and faults and channels within non-porous rocks. Various techniques may be used to increase or concentrate the amount of fluid such as oil in the area of the reservoir, such area being commonly referred to as an enhanced pool.
Generally, during the initial stage of oil production, the forces of gravity and the naturally existing pressure in a reservoir cause a flow of oil to the production well. Thus, primary recovery refers to recovery of oil from a reservoir by means of the energy initially present in the reservoir at the time of discovery. Over a period of time, the natural pressure of a reservoir may decrease as oil is taken at the production well location. In general, as the pressure differential throughout the reservoir and at the production well location decreases, the flow of oil to the well also decreases. Eventually, the flow of oil to the well will decrease to a point where the amount of oil available from the well no longer justifies the costs of production, which includes the costs of removing and transporting the oil. Many factors may contribute to this diminishing flow, including the volume and pressure of the oil reservoir, the structure, permeability and ambient temperature of the formation. The viscosity of the oil, particularly the oil disposed away from the central portion of the production well, the composition of the crude oil, as well as other characteristics of the oil, play a significant role in decreased oil production.
As the amount of available oil decreases, it may be desirable to enhance oil recovery within an existing reservoir by external means, such as through injection of secondary energy sources such as steam or gas into the reservoir to enhance oil flow to the production well location. Such mechanisms tend to forcibly displace the oil in order to move the oil in the direction of the production well. Such methods may also heat the oil in order to increase the oil temperature and its mobility. Such methods, however, often require drilling additional bore holes into the reservoir, heating the secondary materials and flooding the materials into the reservoir, in addition to post processing requirements for removing and filtering the secondary materials from the recovered oil. All of these contribute to additional production costs. Moreover, existing techniques still do not adequately enable complete recovery of all of the oil within the reservoir. Thus, in many cases, oil recovery may be discontinued despite a substantial amount of oil remaining within the reservoir, because extraction of the remaining oil is too expensive or too difficult given the current recovery methods.
Alternative mechanisms for enhancing oil recovery are desired.